In small animal practice, periodontal disease (PD) is among the most prevalent conditions. By the age of two, 80% of dogs and 70% of cats already present some degree of PD. Early diagnosis and treatment, as well as the implementation of preventive strategies, are critical in this disease. Toothbrushing remains the gold standard method for achieving good oral health. However, certain products haveñ proven effective in preventing plaque accumulation. The seaweed Ascophyllum nodosum (AN) has gained worldwide interest as a passive method for oral hygiene in humans. Its use in dogs and cats has demonstrated a reduction in the rate of oral health deterioration, quantitatively assessed through plaque and calculus indices. It has also shown effects in preventing plaque formation and inhibiting calculus development. This study evaluated the efficacy of AN ProDen® supplementation in dogs with PD, being the first research on this product in canines in Montevideo, where ProDen PlaqueOff® powder (Swedencare), based on AN ProDen® and endorsed by the V.O.H.C., is commercially available. The objective was to determine the impact of ProDen PlaqueOff® on PD management, analyzing its effect on dental calculus, plaque, and gingivitis, as well as on selected blood parameters of treated animals. Twelve neutered dogs (males and females) from an animal shelter, age range from 1 to 6 years and diagnosed with grade 1 or 2 PD, were selected. All dogs were fed the same diet and kept under controlled conditions. Dogs were divided into two groups: one treated group receiving ProDen PlaqueOff® for 120 consecutive days, and one untreated control group. The teeth evaluated were: 104, 204, 304, 404, 108, 208, 309 and 409. Calculus, plaque and gingivial indices adapted from Löe and Silness were registered monthly for 4 months. Blood samples were collected from the treated group at days 0 and 120. The treated group had a mean age of 3.4 ± 1 years and a mean weight of 19.8 ± 6 kg, while the control group had a mean age of 3.5 ± 1 years and a mean weight of 19.5 ± 7 kg. Findings indicated significant improvement in calculus (p <0,0001), gingivitis (p <0,0001) and plaque (p=0,0244) indices in the treated group. Changes were observed in blood parameters including calcium (p=0,003) and creatinine (p=0,05), with a tendency (p=0,09) toward variation in thyroxine (T4L) and aspartate aminotransferase (AST) levels, although all values remained within physiological ranges. In summary, ProDen PlaqueOff® supplementation proved effective in managing PD in dogs, highlighting its potential as a therapeutic adjunct. The results of this study support the inclusion of ProDen PlaqueOff® as a valuable tool in periodontal therapy.